Apparatus for providing multimedia services and method thereof

ABSTRACT

Provided are a transmitter and a receiver for providing a multi-layered multimedia service, and a method thereof The transmitter includes: a Multiple Description Coding (MDC) unit configured to perform MDC on at least one source, and to output a description sequence for the at least one source; a Unequal Error Protection (UEP) grouping unit configured to output a UEP description sequence having a different number of description sequences constituting the description sequence according to a UEP level to which an importance level of the at least one source has been reflected; and a transmission code block processor configured to segment the UEP description sequence, to modulate each segmented UEP description sequence, and to generate a transmission block. Therefore, it is possible to ensure graceful degradation and scalability and provide a high-quality multimedia service.

CLAIM FOR PRIORITY

This application claims priority to Korean Patent Application Nos.10-2011-0138404 filed on December 20, 2011, 10-2012-0087811 filed onAug. 10, 2012, and 10-2012-0130780 filed on Nov. 19, 2012 in the KoreanIntellectual Property Office (KIPO), the entire contents of which arehereby incorporated by reference.

BACKGROUND

1. Technical Field

Example embodiments of the present invention relate in general toprovision of multimedia services, and more specifically, to atransmitter and a receiver for providing a multi-layer multimediaservice, and a method thereof.

2. Related Art

With the ultra-high speed of wireless networks and the Internet,video-based multimedia content services have been popularized in abroadcasting and telecommunication converged environment, such as videostreaming, mobile broadcasting, IPTV, etc. In particular, with theintroduction of mobile terminals such as smart phones, demands formobile multimedia services are rapidly increasing.

Multimedia services require provision of various kinds of multimediainformation having different information characteristics. Also, variouskinds of terminals capable of using multimedia services and variouskinds of service qualities capable of implementing for each terminal areprovided.

In order to efficiently cope with such diversity, service scalability isneeded. Also, in mobile broadcasting, since the states of channelscontinue to change, graceful degradation should be ensured in order toavoid abrupt degradation of service quality.

Since the transmitter of a broadcasting system has no information (kindof terminals, required service qualities, channel states, etc.) aboutterminals, it is difficult to provide multimedia services efficientlyaccording to users' requirements.

That is, most of existing broadcasting systems have been designed inconsideration of a terminal in the worst conditions. For example, eMBMSof 3GPP has adopted QPSK modulation and Single Input Single Output(SISO) transmission scheme having the lowest transmission efficiency inconsideration of the case where a terminal has only one receptionantenna and the channel state is very bad.

However, the approach has a problem that even though terminals having aplurality of reception antennas and being in a good channel environmentcan receive information at a high transmission rate, the terminalscannot receive high-quality multimedia services due to a limited amountof transmission information. Accordingly, in order to efficientlyprovide multimedia services, a transmitter has to provide high-qualitymultimedia services, and a terminal has to decide quality of serviceaccording to its performance and channel state.

Scalable video coding (SVC), which is a representative technique forensuring scalability, has been adopted as a standard by manyStandardization Organizations. In the SVC, an input signal isrepresented as multi-layer information having different informationpriorities.

Multimedia information encoded by the SVC scheme is mainly transmittedby a layered modulation (LM)-based transmission method. In the LM-basedtransmission method, a modulated base layer and an enhanced layer aretransmitted at the same time. For example, AT-DMB and MediaFLO use 16QAMto transmit a modulated base layer and an enhanced layer at the sametime. However, in the case of transmitting two or more layers, receptionperformance is degraded due to an increase of inter-layer interference.Also, in the LM-based transmission method, coverage rapidly decreasessince power allocated to the base layer is reduced as the number oflayers increases.

A transmitter that provides high-quality multimedia services is requiredto transmit information at high speed, and for fast transmission, it issuitable that a Multiple Input Multiple Output (MIMO) technology isused. In order to transmit information according to the MIMO technology,the number of reception antennas is required to be equal to or more thanthe number of transmission antennas. However, in conventional mobilebroadcasting, in many cases, since the number of reception antennas of aterminal is less than the number of transmission antennas of a basestation, it is difficult to use the MIMO technology.

SUMMARY

Accordingly, example embodiments of the present invention are providedto substantially obviate one or more problems due to limitations anddisadvantages of the related art.

Example embodiments of the present invention provide a transmitter and areceiver for providing multimedia services while ensuring gracefuldegradation and scalability.

Example embodiments of the present invention also provide a method ofproviding multimedia services while ensuring graceful degradation andscalability.

In some example embodiments, there is provided a transmitter ofproviding a multimedia service in a multimedia service providingapparatus, including: a Multiple Description Coding (MDC) unitconfigured to perform MDC on at least one source, and to output adescription sequence for the at least one source; a Unequal ErrorProtection (UEP) grouping unit configured to output a UEP descriptionsequence having a different number of description sequences constitutingthe description sequence according to a UEP level to which an importancelevel of the at least one source has been reflected; and a transmissioncode block processor configured to segment the UEP description sequence,to modulate each segmented UEP description sequence, and to generate atransmission block.

The transmitter may further include an antenna mapping unit configuredto duplicate the transmission block, to generate a plurality of the sametransmission blocks, and to map the respective transmission blocks to atleast one transmission antenna.

The MDC unit may perform MDC on the at least one source in unit of a sublayer that is divided into a base layer and at least one enhanced layer.

The transmitter may further include a systematic raptor coding unitconfigured to perform systematic raptor coding on each descriptionsequence output from the MDC unit.

The transmission code block processor may include: a code blocksegmenting unit configured to segment each UEP description sequenceoutput from the UEP grouping unit to one or more code blocks; a CyclicRedundancy Check (CRC) attaching unit configured to attach a CRC code toeach code block; a channel coding unit configured to perform channelcoding for each code block to which the CRC code has been attached, andto output a channel-coded code block; and a modulator configured tomodulate each code block output from the channel coding unit, and togenerate the transmission block.

The transmitter may further include a pilot inserting unit configured toinsert a pilot signal for each of the at least one transmission antenna.

In other example embodiments, there is provided a receiver of providinga multimedia service in a multimedia service providing apparatus,including: a Multi Input Multi Output (MIMO) decoding unit configured toreceive a plurality of the same transmission blocks through at least onereception antenna, and to output a demodulated Log Likelihood Ratio(LLR) block which is a LLR block of the transmission block, in unit of atransmission block; a demodulated LLR block combining unit configured tocombine the demodulated LLR block with the preceding demodulated LLRblock, and to output an improved, demodulated LLR block; and a receptioncode block processor configured to perform channel decoding on theimproved, demodulated LLR block, and to output a code block.

The MIMO decoding unit may include: a channel estimator configured togenerate a channel estimated value using a pilot signal received throughthe at least one reception antenna, and to decide an execution order ofMIMO detection; a transmission block regenerator configured to feed theimproved, demodulated LLR block and the code block back from thedemodulated LLR block combining unit and the reception code blockprocessor, respectively, and to generate a regenerated transmissionblock using the improved, demodulated LLR block and the code block; anda MIMO detector configured to perform MIMO detection in unit of thetransmission block with reference to the channel estimated value and theregenerated transmission block, and to output the demodulated LLR block.

The reception code block processor may include: a channel decoding unitconfigured to perform channel decoding on the improved, demodulated LLRblock, and to generate a decode block; a CRC unit configured to receivethe decode block, to check a CRC code of the decode block, and todetermine whether reception has been successfully performed for eachcode block; and a code block buffer unit configured to remove the CRCcode from the decode block, and to output the code block.

The receiver may further include: a received description restoring unitconfigured to receive the code block, and to reconstruct a descriptionsequence; a systematic raptor decoding unit configured to performsystematic raptor decoding on each description sequence, and to outputthe resultant description sequence; and a multiple description decodingunit configured to perform multiple description decoding on thedescription sequence output from the systematic raptor decoding unit,and to restore at last one source.

The multiple description decoding unit may perform multiple descriptiondecoding on the at least one source in unit of a sub layer that isdivided into a base layer and at least one enhanced layer.

In still other example embodiments, there is provided a receiving methodof providing a multimedia service in a multimedia service providingmethod, including: receiving a plurality of the same transmission blocksthrough at least one reception antenna, and outputting a demodulated LogLikelihood Ratio (LLR) block which is a LLR block of the transmissionblock, in unit of a transmission block; combining the demodulated LLRblock with the preceding demodulated LLR block, and outputting animproved, demodulated LLR block; and performing channel decoding on theimproved, demodulated LLR block, and outputting a code block.

According to the transmitter of providing the multimedia service,according to the present embodiment, as described above, it is possibleto provide a high-quality multimedia service using a plurality oftransmission antennas regardless of the number of antennas of areceiver.

Also, the receiver of providing the multimedia service, according to thepresent embodiment, as described above, can decide the quality of amultimedia service by reflecting the performance of the receptionterminal, power consumption, and a user's requirement when the number ofreception antennas is insufficient and a channel state is poor.

BRIEF DESCRIPTION OF DRAWINGS

Example embodiments of the present invention will become more apparentby describing in detail example embodiments of the present inventionwith reference to the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating the configuration of atransmitter according to an embodiment of the present invention;

FIG. 2 is a block diagram illustrating the configuration of atransmission code block processor shown in FIG. 1;

FIG. 3 is a block diagram illustrating the configuration of an antennamapping unit shown in FIG. 1;

FIG. 4 is a conceptual view for describing an environment where atransmitter and a receiver according to embodiments of the presentinvention operate;

FIG. 5 is a block diagram illustrating the configuration of a receiveraccording to an embodiment of the present invention;

FIG. 6 is a block diagram illustrating the configuration of a MultiInput Multi Output (MIMO) decoding unit shown in FIG. 5;

FIG. 7 is a block diagram illustrating the configuration of a receptioncode block processor shown in FIG. 5;

FIG. 8 is a flowchart illustrating a transmission method according to anembodiment of the present invention; and

FIG. 9 is a flowchart illustrating a reception method according to anembodiment of the present invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Example embodiments of the present invention are disclosed herein.However, specific structural and functional details disclosed herein aremerely representative for purposes of describing example embodiments ofthe present invention, however, example embodiments of the presentinvention may be embodied in many alternate forms and should not beconstrued as limited to example embodiments of the present invention setforth herein.

Accordingly, while the invention is susceptible to various modificationsand alternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that there is no intent to limit theinvention to the particular forms disclosed, but on the contrary, theinvention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention. Like numbers referto like elements throughout the description of the figures.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(i.e., “between” versus “directly between”, “adjacent” versus “directlyadjacent”, etc.).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”,“comprising,”, “includes” and/or “including”, when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

The term “transmitter” used in the following description may include abase station, a Node-B, eNode-B, a base transceiver system (BTS), anaccess point, a relay, a femto-cell, etc. Also, the term “receiver” usedin the following description may include a mobile terminal, a mobilestation (MS), user equipment (UE), a user terminal (UT), a wirelessterminal, an access terminal (AT), a terminal, a subscriber unit, etc.

Multiple description coding (MDC) has a characteristic capable ofensuring graceful degradation. That is, since the MDC represents asingle piece of information as several descriptions in consideration ofdata loss during transmission, information can be restored with degradedquality although a part of the descriptions is received. In this case,distortion of information increases in proportion to the number of lostdescriptions.

That is, scalable video coding (SVC) cannot ensure graceful degradation,and the MDC has no scalability. In order to overcome the problem,scalable MDC (or layered MDC) capable of ensuring both scalability andgraceful degradation has been proposed.

The scalable MDC represents an input signal as a plurality of layers,and the individual layers may have different numbers of descriptions torepresent information priorities.

For example, in the SVC or the scalable MDC, the lower layer has ahigher information priority than the upper layer, and if the lower layeris not successfully received, the upper layer cannot be restored.

Accordingly, in order to efficiently transmit layer information havingdifferent information priorities, unequal error protection (UEP)transmission providing different levels of error protection according toinformation priorities is required. For the UEP transmission, a layeredmodulation (LM) transmission method may be used.

In an apparatus and method for providing multimedia services, accordingto the present embodiments, layers may be divided and transmitted,unlike the LM transmission method, in order to transmit informationhaving different information priorities. Also, by differentiating a coderate, a modulation order, and a repetition number according toinformation priorities, the levels of error protection may be adjusted.

Hereinafter, embodiments of the present invention will be described indetail with reference to the appended drawings.

FIG. 1 is a block diagram illustrating the configuration of atransmitter according to an embodiment of the present invention.

Referring to FIG. 1, the transmitter according to the embodiment of thepresent invention includes a MDC unit 100, a systematic raptor codingunit 110, an UEP grouping unit 120, a transmission code block processor130, an antenna mapping unit 140, and a pilot inserting unit 150.

Hereinafter, in description of herein, the MDC unit 100, the systematicraptor coding unit 110, the UEP grouping unit 120, the transmission codeblock processor 130, the antenna mapping unit 140, and the pilotinserting unit 150 are shown as separate parts, however, they may beimplemented as a single physical device or a single module. Also, theMDC unit 100, the systematic raptor coding unit 110, the UEP groupingunit 120, the transmission code block processor 130, the antenna mappingunit 140, and the pilot inserting unit 150 each may be implemented as aphysical device, a plurality of physical devices forming no group, or agroup.

The MDC unit 100 receives at least one source, and performs MDC on thesource to output a plurality of description sequences. A multimediaservice requires provision of various kinds of information havingdifferent characteristics. For example, the information may beinformation about the senses of smell and touch, as well as audio and(3D) video for reality services. Accordingly, the MDC unit 100 mayinclude one or more MDC blocks for respectively encoding sources thatare classified into various kinds of information.

For example, the number of descriptions configuring a descriptionsequence of representing information of a frame may be adjustedaccording to the priority of the corresponding source. That is, thehigher priority of information, the greater number of descriptions.

The respective MDC blocks may code sources with respect to differentcharacteristics of information. Particularly, a scalable MDC block maycode a source requiring scalability. For example, information requiringscalability may be video information. If only the base layer of videoinformation is received, a low resolution of image is restored, and ifall the base and enhanced layers of video information are received, ahigh resolution of image can be restored.

FIG. 1 shows the case where the transmitter provides a multimediaservice configured with M sources.

The first source among the M sources that are input to the MDC unit 100may require scalability. In this case, the first source is set to beinput to a scalable MDC block.

A sub layer may be defined as a base layer and at least one enhancedlayer. Accordingly, the MDC unit 100 may perform MDC on at least onesource in unit of a sub layer that is divided into a base layer and atleast one enhanced layer.

The MDC unit 100 may divide at least one source into a plurality of bitstreams each called “description”, and encode each description. Thenumber of description sequences of the M-th source is defined to beK_(m), wherein K_(m) may include 1. That is, the scalable MDC blockdivides a source into a plurality of bit streams each calleddescription, in unit of a sub layer, and encode each description.

The MDC unit 100 may output sources about information with the samecharacteristics, configuring multimedia, as a plurality of encodeddescription sequences (description data) having correlation. Thereby,even when a part of the plurality of encoded description sequences islost, the sources can be restored with graceful degradation althoughthere is distortion. Here, the description sequence may include at leastone description.

Accordingly, the MDC unit 100 according to the embodiment of the presentinvention can implement both scalability and graceful degradation when amultimedia service is provided.

In more detail, SVC may implement scalability according to theperformance of a receiver, and MDC may implement graceful degradationaccording to loss of transmission information. Also, SVC requires UEPtransmission since there is a difference in importance between baselayers and enhanced layers, whereas MDC requires no UEP transmissionsince there is no difference in importance between descriptions.

Accordingly, scalable MDC may overcome the problems of SVC that coverageis reduced, there are difficulties in MIMO transmission, and the numberof layers is limited due to UEP transmission.

The systematic raptor coding unit 110 performs systematic raptor codingon each of the plurality of encoded description sequences output fromthe MDC unit 100. Also, the systematic raptor coding unit 110 mayperform systematic raptor coding on each of encoded descriptionsequences output for each sub layer from the scalable MDC coding block.

That is, the systematic raptor coding unit 110 may code descriptionsequences so that description sequences lost during transmission can berestored. Also, the systematic raptor coding unit 110 may include one ormore raptor coding blocks for coding the respective encoded descriptionsequences.

For example, the systematic raptor coding unit 110 may output N_(m)pieces of data from K_(m) encoded description sequences for the M-thsource. Here, it may be set that C_(m)>K_(m)/N_(m), and C_(m)>1. Thesystematic raptor coding unit 110 outputs the K_(m) encoded descriptionsequences as they are, and performs raptor coding on (N_(m)−K_(m))description sequences and outputs the results of the raptor coding.

In other words, systematic raptor coding performed by the systematicraptor coding unit 110 is to output N_(m) pieces of data with respect toK_(m) description sequences for a M-th source, in such a manner tooutput (N_(m)-K_(m)) raptor-coded description sequences and K_(m)description sequences as they are.

That is, the systematic raptor coding unit 110 outputs a plurality ofdescription sequences as they are, and additionally outputs apredetermined number of raptor-coded description sequences.

Thereby, the transmitter according to the present embodiment may performsystematic raptor coding in order to reduce delays and power consumptiondue to raptor decoding at a receiver. Also, the transmitter may adjustthe N_(m) value according to the importance level of a source. The upperlimit of the N_(m) value is not specified, however, the upper limit ofthe N_(m) value may need to be specified since the amount oftransmission data increases as the N_(m) value increases.

Also, the systematic raptor coding may be selectively performed.

The UEP grouping unit 120 may output UEP description sequences havingdifferent numbers of descriptions according to a UEP level to which theimportance level of at least one source has been reflected.

For example, by adjusting the number of descriptions configuring adescription sequence or adjusting the length of a description sequence,the importance level of source information may be represented. Thereby,it is possible to apply higher error protection to more importantinformation upon transmission. That is, UEP is a technique of applyingdifferent degrees of error protection according to the importance levelof information upon transmission.

The UEP grouping unit 120 may classify M input description sequencesinto P error protection levels according to the importance levels of thecorresponding information in order to transfer UEP information to thefollowing stage. That is, the UEP grouping unit 120 may represent sourceinformation having different importance levels by differentiating thenumber of descriptions configuring each description sequence ordifferentiating the length of each description sequence, and thentransmit the resultant source information. Here, it may be P≦M.

FIG. 2 is a block diagram illustrating the configuration of thetransmission code block processor 130 shown in FIG. 1.

Referring to FIG. 2, the transmission code block processor 130 includesa code block segmenting unit 131, a CRC attaching unit 132, a channelcoding unit 133, and a modulator 134. The transmission code blockprocessor 130 may segment and modulate the UEP description sequences,and generate transmission blocks.

The transmission code block processor 130 may segment each UEPdescription sequence into code blocks, and process the code blocks sothat a receiver can check whether transmission is successful and correcttransmission errors for each code block.

Also, the transmission code block processor 130 may modulate each codeblock and output a transmission block. That is, the transmission codeblock processor 130 may segment and modulate the UEP descriptionsequences output from the UEP grouping unit 120, and output transmissionblocks.

The code block segmenting unit 131 segments each UEP descriptionsequence output from the UEP grouping unit 120 into code blocks inconsideration of a code rate and a modulation order. That is, the codeblock segmenting unit 131 may segment each UEP description sequence intoa plurality of code blocks each having a smaller unit than the UEPdescription sequence. For example, if a UEP description sequence issegmented into B_(m) code blocks, the M-th source may be segmented intoa total of 1.5N_(m)×B_(m) code blocks.

The CRC attaching unit 132 attaches a CRC code to each code block. TheCRC may mean a method of using a cyclic binary code to detect errorsgenerated upon data transmission.

That is, if the transmitter segments data in unit of a block, attaches acyclic code obtained by specific calculation of a binary polynominal, toeach block at the tail, and transmit the resultant block, a receiverchecks whether the same cyclic code is obtained by the same calculationto thereby determine whether transmission is successful.

Accordingly, the CRC attaching unit 132 may allow a receiver to checkwhether each code block has been successfully transmitted.

The channel coding unit 133 performs channel coding on each code blockto which a CRC code has been attached, and outputs the result of thechannel coding. Particularly, the channel coding unit 133 may encodeeach code block such that errors generated upon transmission of data canbe corrected as well as detected. For example, the channel coding unit133 may use forward error correction.

The modulator 134 may modulate each code block output from the channelcoding unit 133 to generate a symbol, thereby outputting a transmissionblock. The modulator 134 may modulate Q successive coded bits of a codeblock for each code block to generate a symbol, and transmit atransmission block. For example, in QPSK, the Q value may be 2, and in16QAM, the Q value may be 4. That is, the modulator 134 can improvespectral efficiency (bits/Hz) by transmitting a symbol instead of Qbits, wherein the greater the Q value, the higher the spectralefficiency.

FIG. 3 is a block diagram illustrating the configuration of the antennamapping unit 140 shown in FIG. 1.

Referring to FIG. 3, the antenna mapping unit 140 includes a repetitionunit 141 and a mapping unit 142. The antenna mapping unit 140 maygenerate a plurality of the same transmission blocks by duplicating thetransmission block, and map the individual transmission blocks to atleast one transmission antenna.

For example, the antenna mapping unit 140 may map the transmissionblocks to N_(t) transmission antennas, and thus transmit N_(t) streams.

The repetition unit 141 may generate the plurality of the sametransmission blocks by performing repetition with respect to thetransmission block, and the mapping unit 142 may map each of thetransmission blocks in at least one transmission antenna.

For example, the repetition unit 141 may duplicate for each transmissionblock output from the transmission code block processor 130 by apredetermined number R_(m) of times, and output the corresponding numberof the same transmission blocks. Also, by adjusting the predeterminednumber R_(m) of times, the UEP can be differentiated.

In the case of the M-th source, by performing duplication by thepredetermined number R_(m) of times, 1.5N_(m)×R_(m) transmission blocksmay be output. Accordingly, if a receiver successively receives at leastone of the R_(m) transmission blocks, the repetition unit 141 canrestore the corresponding description sequence. Also, in order to ensurestable reception performance, the R_(m) transmission blocks may betransmitted through independent paths or resources (time, frequency,antenna, etc.) as possible.

The mapping unit 142 may perform one-to-one antenna mapping. That is,the mapping unit 142 enables 1.5×R description sequences for a source tobe transmitted through independent radio resources (time or frequency)in order to increase diversity gain.

For example, in order to increase diversity gain, transmission blockscorresponding to the same source are positioned temporally and spatiallydistant from each other, thereby increasing independency.

Also, the mapping unit 142 enables transmission blocks for the samedescription sequence to be transmitted using a radio resource (time orfrequency) having the same characteristics through the same antenna, inorder to provide the characteristics of an erasure channel in unit of adescription sequence. If a transmitted packet (a code block or adescription sequence) is lost during transmission due to noise,interference, congestion, system failure, etc., it can be considered asan erasure channel

Also, the transmitter may further include the pilot inserting unit 150.The pilot inserting unit 150 may insert a pilot signal for eachtransmission antenna so that a receiver can estimate a MIMO channel.

FIG. 4 is a conceptual view for describing an environment where atransmitter and a receiver according to embodiments of the presentinvention operate.

Referring to FIG. 4, a first base station 410 and a second base station411 transmit signals through three transmission antennas. Each of thefirst base station 410 and the second base station 411 may be atransmitter according to an embodiment of the present invention. Thefirst base station 410 forms a first cell, and the second base station411 forms a second cell.

The first and second base stations 410 and 411 may transmit independentsignals, or may cooperate to transmit the same signal. When cooperativebroadcasting is done, the two base stations 410 and 411 may perform thesame transmission function in order to generate the same transmissionsignal.

A first terminal 420 which belongs to the first cell may receive signalsfrom the first base station 410, and consider signals transmitted fromthe second base station 411 as noise. A second terminal 421, which islocated closer to the second base station 411 although it is locatedbetween the first cell and the second cell, receives signals from thesecond base station 411 and considers signals transmitted from the firstbase station 410 as noise.

Also, if the two base stations 410 and 411 perform cooperativebroadcasting of transmitting the same signal, the two base stations 410and 411 may increase reception efficiency by coherent-combining twosignals from themselves.

There are the cases where base stations have the same number oftransmission antennas, and terminals have different numbers of receptionantennas. The first terminal 420 having 4 reception antennas and thesecond terminal 421 having 2 reception antennas may receive signalstransmitted from a base station having 3 transmission antennas.

FIG. 5 is a block diagram illustrating the configuration of a receiveraccording to an embodiment of the present invention.

Referring to FIG. 5, the receiver includes a MIMO decoding unit 200, ademodulated Log Likelihood Ratio (LLR) block combining unit 210, areception code block processor 220, a received description restoringunit 230, a systematic raptor decoding unit 240, and a multipledescription decoding unit 250.

Hereinafter, in description of herein, the MIMO decoding unit 200, thedemodulated LLR block combining unit 210, the reception code blockprocessor 220, the received description restoring unit 230, a systematicraptor decoding unit 240, and a multiple description decoding unit 250are shown as separate parts, however, they may be implemented as asingle physical device or a single module. Also, the MIMO decoding unit200, the demodulated LLR block combining unit 210, the reception codeblock processor 220, the received description restoring unit 230, asystematic raptor decoding unit 240, and a multiple description decodingunit 250 each may be implemented as a physical device, a plurality ofphysical devices forming no group, or a group.

The receiver according to the present embodiment may receive signals inunit of a transmission block, and perform decoding, etc. on the receivedsignals to restore information. The receiver may have A_(r) receptionantennas. That is, a transmitter may transmit signals mapped totransmission antennas in unit of a transmission block, and the receivermay receive the signals through the reception antennas.

The MIMO decoding unit 200 may receive a plurality of the sametransmission blocks through at least one reception antenna, and output adecoded LLR block which is a LLR block of the transmission block in unitof a transmission block.

The decoded LLR block combining unit 210 may combine the decoded LLRblock with the previous decoded LLR block, and output an improved,decoded LLR block. Also, the decoded LLR block combining unit 210 mayfeed the improved, decoded LLR block back to the MIMO decoding unit 200.

The reception code block processor 220 performs channel decoding on theimproved, decoded LLR block, and output a code block. Also, thereception code block processor 220 may feed the code block back to theMIMO decoding unit 200.

The received description restoring unit 230 may receive the code blockto reconstruct a description sequence, and the systematic raptordecoding unit 240 may perform systematic raptor decoding on thedescription sequence and output the result of the systematic raptordecoding.

Also, the multiple description decoding unit 250 may perform multipledescription decoding on the description sequence output from thesystematic raptor decoding unit 240, and restore at least one source.

FIG. 6 is a block diagram illustrating the configuration of the MIMOdecoding unit 200 shown in FIG. 5.

Referring to FIGS. 5 and 6, the MIMO decoding unit 200 may receive aplurality of the same transmission blocks through A_(r) receptionantennas, and output a demodulated LLR block which is a LLR block of thetransmission block in unit of a transmission block.

That is, the MIMO decoding unit 200 may receive a reception signalthrough at least one reception antenna in unit of a transmission block,and output a LLR block for each transmission block. Accordingly, theMIMO decoding unit 200 may output a LLR block in unit of a transmissionblock, and transfer the LLR block to the demodulated LLR block combiningunit 210 which will be described later.

The MIMO decoding unit 200 includes a channel estimator 201, atransmission block regenerator 202, and a MIMO detector 203.

The channel estimator 201 may calculate a channel estimated value anddecide an execution order of MIMO detection, using a pilot signalreceived through at least one reception antenna. That is, the channelestimator 201 may calculate a MIMO channel estimated value, using apilot signal of a reception signal received through at least onereception antenna, in unit of a transmission block.

Also, the channel estimator 201 may decide an execution order of MIMOdetection. For example, the channel estimator 201 may decide anexecution order of MIMO detection in consideration of a channel state, acode rate, and a modulation order.

The transmission block regenerator 202 may receive an improved,demodulated LLR block and a code block fed back, and create aregenerated transmission block using the improved, demodulated LLR blockand the code block.

That is, the transmission block regenerator 202 may regenerate atransmission block, using the improved, improved LLR block that is theoutput of the demodulated LLR block combining unit 210 and the codeblock that is the output of the reception code block processor 220.

For example, the transmission block regenerator 202 may regenerate atransmission block using the fed-back code block, the channel estimatedvalue, and channel coding, modulation, etc. which the transmitter hasused to form the corresponding transmission block.

Also, the transmission block regenerator 202 may perform hard decisionon the improved, demodulated LLR block, and regenerate a transmissionblock using the channel estimated value and modulation, etc. which thetransmission terminal has used to form the corresponding transmissionblock.

The MIMO detector 203 may output a demodulated LLR block through MIMOdetection that refers to the regenerated transmission block in unit of atransmission block.

The MIMO detection may be performed in unit of a transmission block, anda MIMO detection method may be decided according to the output type ofthe transmission block regenerator 202.

First, MIMO detection based on a code block is described. It may bedetermined whether a transmission block has been successfully decodedduring the period of the previous transmission block and stored in thereception code block processor 220. That is, it may be determinedwhether decoding has been successfully performed before decoding of eachtransmission block.

MIMO detection of a first transmission block in the period of a specifictransmission block will be described.

In the case of non-cooperative broadcasting, a received signal accordingto a specific transmission block period has duplicated N_(t)transmission blocks transmitted from a transmitter. MIMO detection withrespect to the first transmission block may be performed by consideringthe remaining (N_(t)−1) transmission blocks except for the correspondingtransmission block as interference and performing MinimumMean-Square-Error (MMSE) estimation to output a demodulated LLR block.

If it is determined that the demodulated LLR block has been successfullyreceived through the demodulated LLR block combining unit 210 and thereception code block processor 220, MIMO detection with respect to thesecond transmission block may be performed.

Meanwhile, if it is not determined that the demodulated LLR block hasbeen successfully received, MIMO detection with respect to the remainingtransmission blocks may be stopped, and a bit for the demodulated LLRblock of the corresponding transmission block may be replaced with “0.”

The transmission block regenerator 202 may regenerate a firsttransmission block using a first code block successfully received. InMIMO detection with respect to the second transmission block, theregenerated first transmission block is removed, MMSE is performed, andthen MIMO detection is performed to output a demodulated LLR block.

Also, the received signal from which the first transmission block hasbeen removed may be stored. If it is determined that the secondtransmission block has been successfully received, MIMO detection with athird transmission block may be performed.

Accordingly, in MIMO detection with respect to a n-th transmissionblock, a (n−1)-th transmission block may be regenerated using a (n−1)-thcode block that has been just successfully received when a receivedsignal from which (n−2) transmission blocks have been removed has beenstored in advance.

That is, in MIMO detection with respect to the n-th transmission block,a currently regenerated (n−1)-th transmission block may be removed froma received signal from which (n2) transmission blocks have been removedand which has been stored in advance, MMSE may be performed, and thenMIMO detection may be performed. By sequentially performing theoperations, MIMO detection with respect to N_(t) transmission blocks maybe performed.

Then, MIMO detection using an improved, demodulated LLR block may bedescribed.

The MIMO detection using the improved, demodulated LLR block is the sameas the MIMO detection using the code block, except for a difference asfollows.

In the MIMO detection using the improved, demodulated LLR block, it isimpossible to determine whether a transmission block has beensuccessively received, since regeneration is performed before channelcoding.

Accordingly, operation of determining whether a current transmissionblock has been successively received in the previous transmission blockperiod is omitted. Also, since whether a transmission block on whichMIMO detection has been currently performed has been successfullyreceived cannot be determined, it is impossible to stop MIMO detectionwhile the MIMO detection is being performed, and it is possible toperform MIMO detection on all of N_(t) transmission blocks in a specifictransmission block period, without any interruption.

Also, MIMO detection when several base stations cooperate forcooperative broadcasting is similar to MIMO detection when a single basestation performs broadcasting, except for a difference as follows.

When several base stations perform cooperative broadcasting, since areceived signal in a specific transmission block period includesduplicated transmission blocks from the base stations, interference oftransmission signals from all the base stations may be removed from thereceived signal, using the regeneration outputs for transmission blocksfrom the respective base stations. Then, coherent combining is performedon the received signal from which interference has been removed, so thata signal with an improved Signal-to-Noise Ratio (SNR) may be generated.

FIG. 7 is a block diagram illustrating the configuration of thereception code block processor 220 shown in FIG. 5.

Referring to FIG. 7, the reception code block processor 220 includes achannel decoding unit 221, a CRC unit 222, and a code block buffer 223.

The reception code block processor 220 may output a code block for eachtransmission block. Also, the reception code block processor 220 maycorrect transmission errors and determine whether transmission has beensuccessfully performed for each code block.

The channel decoding unit 221 may perform channel decoding on animproved, demodulated LLR block to generate a decode block. That is, thechannel decoding unit 221 may perform forward error correction using animproved, demodulated LLR block. Accordingly, the channel decoding unit221 may generate a decode block decided through forward errorcorrection.

The CRC unit 222 may receive the decode block, and check a CRC code todetermine whether reception has been successfully performed for eachcode block.

The code block buffer 223 may remove the CRC code from the decode blockto generate a code block, output and store the code block, and feed thecode block back to the MIMO decoding unit 200.

Referring to FIG. 5 again, the received description restoring unit 230reconstructs a description sequence using the code block. The receiveddescription restoring unit 230 may reconstruct, when receiving all codeblocks configuring a description sequence, a description sequence usingthe code blocks. If the received description restoring unit 230determines that any one of the received code blocks has an error, thereceived description restoring unit 230 may output the correspondingdescription to be reconstructed, as an erased description. The eraseddescription cannot be used to restore a transmission description, butcan represent information about which description has been erased.

The systematic raptor decoding unit 240 perform systematic raptordecoding on each description sequence. That is, the systematic raptordecoding unit 240 performs no raptor decoding if all descriptionsequences not raptor-coded have been successfully received, and performsraptor decoding of sequentially adding raptor-coded descriptionsequences if there is an erased description sequence among descriptionsequences not raptor-coded, to thereby restore the erased descriptionsequence. Accordingly, the systematic raptor decoding unit 240 may checkwhether any one of description sequences transmitted from a transmitterhas been erased.

For example, in the case of a M-th source, the systematic raptordecoding unit 240 may check whether any one of K description sequenceshas been erased. If all of the K_(m) description sequences have beensuccessfully received, the systematic raptor decoding unit 240 mayoutput the K_(m) description sequences without any modification, therebyreducing time delay and power consumption due to decoding. Also, ifthere is an erased description sequence among the K_(m) transmissiondescriptions, raptor decoding is performed by adding descriptionsequences on which raptor decoding has been performed. At this time, byadding description sequences on which raptor coding has been performeduntil all of the K_(m) description sequences are successfully decoded,raptor decoding is performed. Also, the systematic raptor decoding unit240 may include at least one raptor decoding block for performing raptordecoding for each description sequence.

The receiver according to the present embodiment further includes amultiple description decoding unit 250 for decoding descriptionsequences output from the systematic raptor decoding unit 240 to restoreat least one source. That is, the multiple description decoding unit 250performs MDC-decoding on description sequences encoded by the multipledescription coding unit 100 of a transmitter to restore a source. Also,in the case of a description sequence decoded in unit of a sub layer bya scalable MDC coding block of a transmitter, the multiple descriptiondecoding unit 250 may finally restore a upper layer of a restoreddescription using a lower layer of the restored description. That is,the multiple description decoding unit 250 may perform multipledescription decoding on at least one source in unit of a sub layerconfigured with a base layer and at least one enhanced layer.Accordingly, the multiple description decoding unit 250 may include oneor more MDC decoding blocks capable of respectively decoding sourcesthat are classified into various kinds of information, and a scalableMDC decoding block for decoding sub layer-based descriptions.

FIG. 8 is a flowchart illustrating a transmission method for providing amultimedia service, according to an embodiment of the present invention.

The transmission method according to the present embodiment performsmultiple description encoding on at least one source, and duplicatelytransmits descriptions using one of various channel coding methods,thereby allowing broadcast MIMO transmission with graceful degradation.

Referring to FIG. 8, the transmission method includes: performing MDC tooutput description sequences (S810); reflecting the importance level ofeach source to output UEP description sequences (S820); generatingtransmission blocks (S830); and mapping the respective transmissionblocks to transmission antennas (S840).

In operation S810, MDC may be performed on at least one source, and adescription sequence for the at least one source may be output.

Also, in operation S810, the source may be subject to MDC in unit of asub layer that is divided into a base layer and at least one enhancedlayer.

Then, in operation S820, UEP description sequences having differentnumbers of descriptions according to a UEP level to which the importancelevel of the source has been reflected may be output.

In operation S830, each UEP description sequence may be divided intocode blocks, a CRC code is attached to each code block, channel codingmay be performed on each code block to which the CRC code has beenattached, and the channel-coded code block may be output. Then, thechannel-coded code block is modulated, so that a transmission block maybe generated.

In operation S840, the transmission block may be duplicated to generatea plurality of the same transmission blocks, and the respectivetransmission blocks may be mapped to at least one transmission antenna.Also, a pilot signal may be inserted for each transmission antenna.

Also, the transmission method may further include operation ofperforming systematic raptor coding on each description sequence.

FIG. 9 is a flowchart illustrating a reception method for providing amultimedia service, according to an embodiment of the present invention.

The reception method according to the present embodiment includes:outputting a demodulated LLR block (S910); outputting an improved,demodulated LLR block (S920);

outputting a code block (S930); receiving the code block to reconstructa description sequence (S940); performing systematic raptor coding(S950); and performing multiple description decoding (S960).

In operation S910, a plurality of the same transmission blocks may bereceived through at least one reception antenna, and a demodulated LLRblock which is a LLR block of the transmission block may be output.

In detail, in operation S910, a channel estimated value may be createdand an execution order of MIMO detection may be decided, using a pilotsignal received through at least one reception antenna, an improved,demodulated LLR block and a code block fed back may be received, and aregenerated transmission block may be created using the improved,demodulated LLR block and the code block. Thereby, a demodulated LLRblock may be output through MIMO detection that refers to the channelestimated value and the regenerated transmission block in unit of atransmission block.

In operation S920, the demodulated LLR block may be combined with theprevious demodulated LLR block to output an improved, demodulated LLRblock.

In operation S930, channel decoding may be performed on the improved,demodulated LLR block to generate a code block.

In detail, in operation S930, channel decoding may be performed on theimproved, demodulated LLR block to generate decode blocks, and a CRCcode is checked to determine whether reception has been successfullyperformed for each code block. Then, the CRC codes may be removed fromthe decode blocks to output code blocks.

In operation S940, the code blocks may be received to reconstructdescription sequences. That is, description sequences may be restoredthrough a combination of the code blocks.

In operation S950, systematic raptor decoding may be performed on eachdescription sequence, and the resultant description sequences may beoutput.

In operation S960, multiple description decoding may be performed on thedescription sequences subject to systematic raptor decoding to restoreat least one source. In operation S960, multiple description decodingmay be performed on the at least one source in unit of a sub layer thatis divided into a base layer and at least one enhanced layer.

The transmission method and the reception method as described above areperformed by the transmitter and the receiver according to theembodiments of the present invention, respectively, and will be moreclearly understood with reference to the above description related tothe transmitter and the receiver.

The transmitter may duplicately transmit different description sequencesusing a plurality of antennas, and the receiver may perform receptionaccording to its capability and channel state.

For example, a terminal having a great number of antennas and being in agood channel state receives all description sequences to restore ahigh-quality signal, and a terminal having a small number of antennasand being in a poor channel state restores a low-quality signal since itcannot receive a part of transmitted description sequences.

In this specification, the transmitter transmits signals through aplurality of transmission antennas, and the receiver has no limitationon the number of antennas, which may be called Multi Input VariableOutput (MIVO) broadcasting.

While the example embodiments of the present invention and theiradvantages have been described in detail, it should be understood thatvarious changes, substitutions and alterations may be made hereinwithout departing from the scope of the invention.

What is claimed is:
 1. A transmitter of providing a multimedia servicein a multimedia service providing apparatus, comprising: a MultipleDescription Coding (MDC) unit configured to perform MDC on at least onesource, and to output a description sequence for the at least onesource; a Unequal Error Protection (UEP) grouping unit configured tooutput a UEP description sequence having a different number ofdescription sequences constituting the description sequence according toa UEP level to which an importance level of the at least one source hasbeen reflected; and a transmission code block processor configured tosegment the UEP description sequence, to modulate each segmented UEPdescription sequence, and to generate a transmission block.
 2. Thetransmitter of claim 1, further comprising an antenna mapping unitconfigured to duplicate the transmission block, to generate a pluralityof the same transmission blocks, and to map the respective transmissionblocks to at least one transmission antenna.
 3. The transmitter of claim1, wherein the MDC unit performs MDC on the at least one source in unitof a sub layer that is divided into a base layer and at least oneenhanced layer.
 4. The transmitter of claim 1, further comprising asystematic raptor coding unit configured to perform systematic raptorcoding on each description sequence output from the MDC unit.
 5. Thetransmitter of claim 1, wherein the transmission code block processorcomprises: a code block segmenting unit configured to segment each UEPdescription sequence output from the UEP grouping unit to one or morecode blocks; a Cyclic Redundancy Check (CRC) attaching unit configuredto attach a CRC code to each code block; a channel coding unitconfigured to perform channel coding for each code block to which theCRC code has been attached, and to output a channel-coded code block;and a modulator configured to modulate each code block output from thechannel coding unit, and to generate the transmission block.
 6. Thetransmitter of claim 2, further comprising a pilot inserting unitconfigured to insert a pilot signal for each of the at least onetransmission antenna.
 7. A receiver of providing a multimedia service ina multimedia service providing apparatus, comprising: a Multi InputMulti Output (MIMO) decoding unit configured to receive a plurality ofthe same transmission blocks through at least one reception antenna, andto output a demodulated Log Likelihood Ratio (LLR) block which is a LLRblock of the transmission block, in unit of a transmission block; ademodulated LLR block combining unit configured to combine thedemodulated LLR block with the preceding, demodulated LLR block, and tooutput an improved, demodulated LLR block; and a reception code blockprocessor configured to perform channel decoding on the improved,demodulated LLR block, and to output a code block.
 8. The receiver ofclaim 7, wherein the MIMO decoding unit comprises: a channel estimatorconfigured to generate a channel estimated value using a pilot signalreceived through the at least one reception antenna, and to decide anexecution order of MIMO detection; a transmission block regeneratorconfigured to feed the improved, demodulated LLR block and the codeblock back from the demodulated LLR block combining unit and thereception code block processor, respectively, and to generate aregenerated transmission block using the improved, demodulated LLR blockand the code block; and a MIMO detector configured to perform MIMOdetection in unit of the transmission block with reference to thechannel estimated value and the regenerated transmission block, and tooutput the demodulated LLR block.
 9. The receiver of claim 7, whereinthe reception code block processor comprises: a channel decoding unitconfigured to perform channel decoding on the improved, demodulated LLRblock, and to generate a decode block; a CRC unit configured to receivethe decode block, to check a CRC code of the decode block, and todetermine whether reception has been successfully performed for eachcode block; and a code block buffer unit configured to remove the CRCcode from the decode block, and to output the code block.
 10. Thereceiver of claim 7, further comprising: a received descriptionrestoring unit configured to receive the code block, and to reconstructa description sequence; a systematic raptor decoding unit configured toperform systematic raptor decoding on each description sequence, and tooutput the resultant description sequence; and a multiple descriptiondecoding unit configured to perform multiple description decoding on thedescription sequence output from the systematic raptor decoding unit,and to restore at last one source.
 11. The receiver of claim 11, whereinthe multiple description decoding unit performs multiple descriptiondecoding on the at least one source in unit of a sub layer that isdivided into a base layer and at least one enhanced layer.
 12. Areceiving method of providing a multimedia service in a multimediaservice providing method, comprising: receiving a plurality of the sametransmission blocks through at least one reception antenna, andoutputting a demodulated Log Likelihood Ratio (LLR) block which is a LLRblock of the transmission block, in unit of a transmission block;combining the demodulated LLR block with the preceding demodulated LLRblock, and outputting an improved, demodulated LLR block; and performingchannel decoding on the improved, demodulated LLR block, and outputtinga code block.
 13. The receiving method of claim 12, wherein theoutputting of the demodulated LLR block comprises: generating a channelestimated value using a pilot signal received through the at least onereception antenna, and deciding an execution order of MIMO detection;feeding the improved, demodulated LLR block and the code block back, andgenerating a regenerated transmission block using the improved,demodulated LLR block and the code block; and performing MIMO detectionin unit of the transmission block with reference to the channelestimated value and the regenerated transmission block, and outputtingthe demodulated LLR block.
 14. The receiving method of claim 12, whereinthe outputting of the code block comprises: performing channel decodingon the improved, demodulated LLR block, and generating a decode block;receiving the decode block, checking a CRC code of the decode block, anddetermining whether reception has been successfully performed for eachcode block; and removing the CRC code from the decode block, andoutputting the code block.
 15. The receiving method of claim 12, furthercomprising receiving the code block and reconstructing a descriptionsequence; performing systematic raptor decoding on each descriptionsequence, and outputting the resultant description sequence; andperforming multiple description decoding on the description sequenceoutput after subjected to the systematic raptor decoding, and restoringat last one source.
 16. The receiving method of claim 15, wherein therestoring of the at least one source comprises performing multipledescription decoding on the at least one source in unit of a sub layerthat is divided into a base layer and at least one enhanced layer.